Power operated electro-chemical fixture



Aug. 12, 1969 5.o. KRUEGER 3,461,059

POWER OPERATED ELECTRO-CHEMICAL FIXTURE Filed Oct. l0, 1966 United States Patent O U.S. Cl. 204-297 Claims ABSTRACT OF THE DISCLOSURE An electro-chemical grinding machine having an electrically conductive, rotatable table with a depending annular skirt thereon. An annular extending current conducting brush means is arranged substantially in a circle and in sliding engagement with the lower side of the table and radially within the skirt thereof. The brush means is positioned on a brush carrier which is received within an annular recess formed in the table as dened by the depending skirt. The table skirt protects the brush means and the portion of the underside of the table contacted by the brush means from serious attack by the electrolyte.

This invention relates to a work-holding fixture, and it particularly relates to an indexable rotary fixture adapted for the positioning of a workpiece in successive positions with respect to an electro-chemical (electrolytic) grinding machine.

While electro-chemical grinding equipment has been known for several years, the design of fixturing for same has continued to present ditiiculties. Among these has been the design of xturing which would handle rates of production as high as those of which the machine is capable. This requires that the unloading and reloading of one yworkpiece position take place while a workpiece in another position is being ground with said operations being performed without sacrifice of operator convenience or safety. While turret type fixtures have been previously utilized to obtain high production rates, tboth in conventional grinding and in electro-chemical grinding, there has remained a considerable area for improvement, particularly in view of the space limitations which must be met to fit the fixture into the relatively small and restricted area in the electrolyte pan in front of the grinding wheel. Further, the fixture must operate effectively under the following conditions: (1) low vol-tage on the workpieces, seldom if ever over volts and preferably less, (2) high amperages through the workpieces, often as high as 500 to 3000 amperes and (3) corrosive electrolytes in the grinding areas. It is necessary for the electrical potential to be applied to the workpiece through the relatively moving parts of a movable worktable and if a corrosive electrolyte enters between the relatively moving surfaces of the table and eiiects sufhcient corrosion thereof, then at the low voltages utilized the table parts will be unable to conduct the necessary high amperages.

Accordingly, the objects of the invention include:

(1) To provide an indexable fixture for use in electrochemical grinding machines, which fixture will be indexable conveniently and accurately, fit into the limited available space in the pan of an electro-chemical grinding machine, and yet which will provide ample protection of ICC the current conducting surfaces against corrosive attack by the electrolyte.

(2) To provide a fixture, as aforesaid, which will be particularly adaptable for use in low voltage electrochemical grinding operations, such as at voltages of not over 10 or l5 volts but which will successfully transmit to the workpieces amperages of the order of 500 to 3000 amperes.

(3) To provide apparatus, as aforesaid, which will be of sufficient mechanical simplicity as to be capable of relatively economical manufacture.

(4) To provide apparatus, as aforesaid, which will be of sufficient mechanical simplicity as to be capable of easy and convenient cleaning from time to time as required for the purposes of good maintenance.

(5) To provide apparatus, as aforesaid, which can be conveniently operated by any means capable of effecting rotation of the table, such as a pressure fluid cylinder.

(6) To provide apparatus, as aforesaid, wherein a standard carbon brush or brushes can be used to conduct current to the table.

Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following description and inspecting the accompanying drawings.

In the drawings:

FIGURE 1 is a central sectional View through an apparatus embodying the invention.

FIGURE 2 is a sectional View, partially broken away, taken on the line II--II of FIGURE 1.

GENERAL DESCRIPTION In general, the invention comprises an electrically conductive, rotatable table having a depending annular skirt. An annular extending current-conducting brush means is arranged substantially in a circle and is in sliding engagement with the lower side of the table and radially within the skirt thereof. If desired, a plurality of individual brushes can be used as required to conduct Ithe desired current to the table. The skirt will protect the brushes and the portion of the underside of the table contacted by the brushes from serious attack by the electrolyte.

DETAILED DESCRIPTION Referring now to the drawings, there is shown a horizontal electrically conductive table 1 which is connected to, or is integral with, a downwardly extending cylindrical post 2. The post 2 is supported for rotative movement on and by vertically spaced-apart bearings 3 and 4. The bearings 3 and 4 are received and supported within a generally cylindrical opening 6 in an upstanding hollow boss 7. The boss 7 is connected to or, as shown, is integral with and extends upwardly from, a base 8. An insulating sleeve 9 is positioned between the inner races of the bearings 3 and 4 and the post 2 to protect said bearings from corrosion which might be caused by current flow through the parts thereof.

The lower end of the post 2 has suitable drive means, such as a gear 10, secured thereto. The gear 10 is engaged by a reciprocable rack 11 so that said gear and thereby the post 2 and table 1 can be rotated by reciprocable movement of said rack. Said rack is mounted for reciprocation in a guide structure 12 and it can be reciprocated by any convenient means, such as a piston (not shown) which is reciprocable in a fluid pressure cylinder 13. The

gear is made of insulating material whereby the table 1 and post 2 are insulated from the base 8 and the rack 11.

The gear 10 is hollow and is drivingly connected to the post 2 by a key 14. The gear is closed at its lower end by an annular plate 15. A bolt 17 extends through the central opening in the plate and is threaded into the post 2 whereby the parts are secured in place.

The table 1 has an annular skirt 18 extending downwardly therefrom in a zone spaced radially outwardly from the post 2 whereby to provide a downwardly opening recess, here a channel recess 19. A current-conducting brush means here being illustrated as a plurality of brushes 21, such as copper-carbon brushes, is arranged for contacting the underside of table 1 within the recess 19. The brushes 21 are supported in an annular brush carrier 22 whose external diameter preferably has only a minimum clearance with the internal diameter of the skirt 18. The brush carrier 22 has a series of circumferentially spaced cylindrical pockets 23 and each pocket has a brush 21 vertically slideably supported therein. The brushes 21 are continuously urged upwardly by springs 24 so that said brushes slideably contact the underside of the table 1 within the recess 19. A conductor 26 is connected to each brush and said conductor is secured to the brush carrier 22 by a set screw 27 and a brass plug 30 whereby said conductors have a good electrical connection with said brush carrier. An electrically conductive plate 28 is mechanically and electrically connected to brush carrier 22 by screws 29. One or more supply cables 35 are mechanically and electrically connected to the plate 28 for supplying electrical potential to the brush carrier, the number and size of the cables being selected to provide the necessary current for the electrolytic grinding operation to be carried out,

A cylindrical sleeve 31 of insulating material is sleeved over the upper end of boss 7 and its lower end rests on a shoulder 32 on said boss. The upper end of the sleeve 31 extends above the upper end of the boss. The brush carrier 22 has a radially inwardly extending flange 33 at its upper end and said brush carrier is press litted onto the sleeve 31 so that said flange rests on the upper end of the sleeve whereby said brush carrier is supported thereby and is insulated from the boss 7.

It will be understood that suitable work holders for holding workpieces, such as one or more vises, will be mounted on the upper surface of table 1 in a conventional, well understood manner, but since this forms no part of the present invention, the same have been omitted from the drawing.

The upper end of the bnish carrier 22 is disposed within OPERATION While the operation of the apparatus has been somewhat indicated above, it will be reviewed in the interest of insuring a complete understanding of the invention.

The base 8 will be fastened to the feed table (not shown) of an electrolytic grinding machine in any convenient manner, said feed table, for example, being the feed table of the machine shown in Patent No. 2,922,258. The workpiece will be mounted on the table 1 by any convenient vise such as the vise shown in Patent No. 2,922,258, for presentation in the desired attitude to the electrolytic grinding wheel. Suitable potential will be supplied to the cables 35 in the manner already well known in electrolytic grinding apparatus. As the grinding operation proceeds, electric current is supplied from the cables 35 through the plate 28 and thence through the annular brush carrier 22 to the brushes 2l. The current then flows to the table 1 and thence through the vise to the workpiece. The electrolytic fluid which is supplied in the required amount to the workpiece flows across the table and downwardly from the skirt 18 and is prevented by said skirt from contacting the underside of the table within the recess 19 and corroding same.

The bearings 3 and 4 are protected from corrosion by electrical current by the insulators 9 and 31. The rack 11 is insulated from current flow by the insulative gear 10.

Although a particular preferred embodiment of the invention has been disclosed above in detail for illustrative purposes, it will be recognized that variations or modifications of such disclosure, which come within the scope of the appended claims, are fully contemplated.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a work-holding device for use with an electrochemical apparatus, such as an electrolytic grinding machine, the combination comprising:

a base;

a table of electrically conductive material spaced upwardly from said base and means for rotatably supporting said table on said base;

an annular skirt extending downwardly from said table;

and

current-conducting brush means positioned radially inside of said skirt and slideably contacting the underside of said table for conducting current thereto, whereby said brush means and the portion of the table contacted thereby are protected by said skirt from the electrolyte used in the electrolytic operation.

2. The device defined in claim 1, in which said brush means defines a substantially annular extending contact zone and simultaneously slideably contacts said table in at least a plurality of circumferentially spaced locations.

3. The device defined in claim 1, in which said base has an upstanding boss extending close to the underside of the table and being located radially inwardly from said brush means, and a brush carrier associated with said annular boss for supporting sid brush means.

4. The device defined in claim 3, in which said brush carrier is annular and has a recess in the upper surface thereof for receiving said brush means.

5. The device defined in claim 3, in which said brush carrier is annular and has a plurality of circumferentially spaced pockets in the upper surface thereof for receiving said brush means, and in which said brush means comprises a plurality of current-conducting brushes positioned within said plurality of circumferentially spaced pockets.

6. The device defined in claim 1, in which the means for rotatably supporting the table includes a depending post on said table located radially inwardly of said brush means and bearing means on said base for rotatably supporting said post.

7. The device defined in claim 6, including pinion means secured to said post, rack means drivingly engaging said pinion means for effecting rotation thereof, and guide means associated with said base for supporting said rack for reciprocable movement.

8. The device defined in claim 6, including a sleeve of electrical insulation material interposed between said post and said bearing means.

9. The device defined in claim 1, in which said table has a circular post extending downwardly from the underside thereof at the center thereof, said base having an upstanding annular boss surrounding and spaced radially outwardly from said post, said boss extending close to the underside of `said table, bearing means mounted on said boss and located in the space between said boss and said post and a first sleeve of insulating material between said bearing means and said post, said bearing means supporting said table for rotation with respect to said base, an annular brush carrier surrounding the ripper end of said boss and positioned between said boss and said skirt, a second sleeve of insulating material between said brush carrier and said boss and cooperating means on said brush carrier and said sleeve for supporting said brush carrier on said boss, said skirt being vertically overlapped with the upper end of said brush carrier and .being closely radially spaced therefrom, said brush carrier having an upwardly 5 opening recess therein, said brush means being vertically slideably disposed in said recess and spring means in said recess for urging said brush means upwardly.

10. The device dened in claim 9, in which said brush means defines a substantially annular extending contact area and simultaneously slideably contacts said table in at least a plurality of circumferentially spaced locations.

References Cited UNITED STATES PATENTS 1/1960 Robisehung 204-297 XR 6/ 1968 Ellis et al. 204--224 XR U.S. C1. X.R. 2 04-286 

